Project Summary/Abstract Socket pistoning, defined as the axial movement of the residual limb within a prosthetic socket, leads to discomfort and skin damage such as blisters, skin breakdown, and callouses in Veterans with an amputation. Most previous research has assessed pistoning statically, but this does not represent the pistoning that takes place during typical activities encountered in daily life. Two previous studies have assessed pistoning dynamically, but required expensive equipment and socket modification. Developing an inexpensive tool that does not require socket modification and can accurately measure socket pistoning dynamically could improve socket comfort and fit for Veterans with amputations, allowing them to regain the greatest possible level of functional ability and activity. The purpose of the proposed project is to design, develop, validate, and clinically implement a novel measurement device that is inexpensive, requires no socket modification, and accurately and quantitatively measures socket pistoning in Veterans with transtibial and transfemoral amputations. Using technology such as non-contact potentiometers and wireless transceivers, an accurate, portable, and inexpensive prototype has been developed. The first aim of the proposed work is to further design and develop this dynamic socket pistoning measurement device so that it can be used in a clinical setting. Five devices and a user interface will be assembled and calibrated. The devices will be small (7cm x 4cm x 3cm), inexpensive (cost <$500), portable (battery-powered and wireless), and require no socket modification. The second aim is to validate the socket pistoning measurement device. To assess dynamic socket pistoning, data will be collected simultaneously from the socket pistoning measurement device, dynamic stereo radiography system, and Vicon motion capture system, while an anthropomorphic representative limb is moved up and down at 1-2 Hz within a 40 mm range inside a custom-fabricated socket, an axial movement typical for walking. When the socket pistoning measurement device results are less than 2 mm different from the dynamic stereo radiography and Vicon systems, and have a signal drift of less than 1% over five minutes, the device will be implemented in the clinic. The final aim is to clinically implement the socket pistoning measurement device on Veterans with an amputation at the VA Eastern Colorado Health Care System Jewell Regional Amputation Clinic to practically assess system design and function. Three prosthetists will implement the socket pistoning measurement device during their regularly scheduled appointments on 20 Veterans with transtibial or transfemoral amputations. Both the patients and prosthetists will evaluate the device for ease of use, comfort and applicability. The accurate quantification of socket pistoning dynamically and in a clinical setting will provide an objective measure of socket comfort and fit; thus giving beneficial information to prosthetists and researchers that could improve socket fabrication techniques and assessment of socket comfort. Properly fitting sockets and the reduction of socket pistoning have the potential to reduce residual limb skin problems, make ambulation more comfortable, and encourage a more active lifestyle among Veterans with a leg amputation.